I am also looking for a small car. I have shortlisted the Daihatsu Mira 2007, 08 or 09 model with CVT transmission.
For your budget I would suggest a 2006 or 2007 Daihatsu Mira. 2006 is the old shape. 2007-10 shape looks better. I think for your budget you will be able to find a 2007 Mira. But go for manual transmission if you want best economy, CVT gearbox is the next best thing if you are looking for low fuel consumption, but it is only available in Mira Custom and Mira X Limited. Mira Custom is beyond your price range and Mira X limited is very hard to find. If not CVT transmission then the next best thing is a 4 speed automatic transmission. Avoid the 3 speed automatic.
The reason I am recommending Mira is because you see a lot of it on the roads these days, which means that in future there is greater chance of availability of spares as compared to cars like Esse. Mira's Engine is KF-VE which is the same engine as in Daihatsu Esse, Move, Mira Gino, Conte, Tanto and Exe.
If you need more info do let me know.